Agricultural seeders are used to place seed and fertilizer in the soil to plant a crop. It is necessary to place the seed at a substantially consistent depth beneath the surface of the soil. Opener arms of various configurations typically extend downward from the seeder frame with a seed furrow opener mounted to the opener arm and adapted to engage the soil to make a seed furrow into which the seed is deposited. Typically, the furrow opener pushes soil to one or both sides and seed is deposited close behind the furrow opener so that the pushed aside soil can then fall back in on top of the seed. A packer wheel is typically provided following the seed furrow opener and oriented to roll over the seed furrow to pack the soil that has fallen back over the seed and encourage seed germination.
In order to maintain a consistent seed depth, agricultural seeding implements have been designed to provide an individual independently movable furrow opener assembly for each furrow being seeded. A popular furrow opener assembly comprises a trailing arm pivotally attached at a front end thereof to the seeder such that the arm extends generally rearward and downward from the frame and can pivot up and down with respect to the seeder frame. A packer wheel is rotatably attached to support the rear end of the trailing arm. A seed furrow opener is attached to the trailing arm ahead of the packer wheel such that the vertical position of the bottom of the seed furrow opener with respect to the bottom of the packer wheel can be fixed at a desired location to set the depth of the seed furrow. A bias element is provided to push or pull downward on the trailing arm to engage the seed furrow opener in the soil and force the packer wheel against the ground.
The furrow opener assemblies are spaced laterally along the width of the implement by mounting the front ends of the trailing arms to lateral frame members of the implement.
The packer wheel pushes down the soil of the seed in the seed furrow and the bottom of the packer wheel corresponds to the soil surface. The depth of the seed furrow is substantially determined by the vertical distance that the bottom end of the seed furrow opener extends below the bottom of the packer wheel. Such a trailing arm seed furrow opener assembly is disclosed for example in U.S. Pat. No. 7,412,933 to Bourgault et al., particularly in FIG. 1 thereof, and in U.S. Pat. No. 5,396,851 to Beaujot.
The bias element used to apply the downward bias force is typically provided by a hydraulic cylinder and it is convenient to also use this same hydraulic cylinder to raise and lower the furrow opener assemblies. In an operating mode, pressurized hydraulic fluid is directed into an operating end of the hydraulic cylinder to move the hydraulic cylinder in a direction such that same forces the furrow opener assembly downward to an operating position where same engages the ground, and in a transport mode, pressurized hydraulic fluid is directed into an opposite transport end of the hydraulic cylinder to move the hydraulic cylinder in the opposite direction and raise the furrow opener assembly to a raised transport position where the packer wheel and furrow opener are above the ground. In some configurations the hydraulic cylinder extends in the operating mode and retracts in the transport mode, and in other configurations the opposite occurs.
When in the operating mode, pressurized hydraulic fluid is constantly being directed into the operating end of the hydraulic cylinder to maintain a substantially constant bias force on the assembly. The source of pressurized hydraulic fluid is operative to maintain a substantially constant pressure of fluid in the cylinder, and also to allow fluid to move into and out of the cylinder to allow the furrow opener assembly to move up and down to follow the terrain.
In the transport mode however, pressurized hydraulic fluid enters the transport end of the hydraulic cylinder until the furrow opener assembly is fully raised, and the hydraulic cylinder is fully extended or retracted as the case may be. Once the fully raised position is reached, a valve is typically operative to close the connection to the source of pressurized hydraulic fluid, such that fluid in the hydraulic cylinder is blocked from exiting the cylinder and the weight of the assembly is supported by the non-compressible fluid in the cylinder.
A problem occurs with age and wear of the hydraulic seals in the hydraulic cylinder as hydraulic fluid can leak past the seals, either internally or externally, such that the furrow opener assemblies creep down. The operator can operate the valve to direct pressurized hydraulic fluid into the transport end of the hydraulic cylinder periodically to raise any partially lowered assemblies to the fully raised transport position. If this downward creep goes unnoticed, it can lead to equipment damage during transport, or damage to adjacent vehicles while traveling on public roads. Because of the typical parallel configuration of the multiple opener assemblies on a single toolbar, a single failed seal causing a leak on a single cylinder could result in the failure of all of the assemblies to be held in the transport position.
Agricultural equipment manufacturers have been working to minimize the leak down of the opener assemblies with the addition of multiple backup isolation valves in an attempt to extend transport periods with limited success.